Methods and systems for a vehicle driveline control during varying driving conditions

ABSTRACT

Systems and methods for improving operation of a hybrid vehicle are presented. In one example, driveline operating modes may be adjusted in response to driving surface conditions. The approaches may improve vehicle drivability and reduce driveline degradation.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/652,340, entitled “METHODS AND SYSTEMS FOR A VEHICLEDRIVELINE CONTROL DURING VARYING DRYING CONDITIONS,” filed on Oct. 15,2012, which claims priority to U.S. Provisional Patent Application No.61/643,156, entitled “METHODS AND SYSTEMS FOR A VEHICLE DRIVELINE,”filed on May 4, 2012, the entire contents of each of which are herebyincorporated by reference for all purposes.

FIELD

The present description relates to a system and methods for improvingdrivability and fuel economy of a vehicle. The methods may beparticularly useful for engines that are selectively coupled to anelectrical machine and a transmission.

BACKGROUND AND SUMMARY

Hybrid vehicles potentially offer improvements to fuel efficiency andvehicle driving range over non-hybrid vehicles. One way to furtherimprove fuel efficiency is to cease operating the engine. However, whenengine operation is ceased, less than full torque output of the vehicledriveline may be available to avoid undesirable road conditions.Therefore, stopping engine rotation to conserve fuel may decrease thepossibility that a driver will have a desired amount of driveline torqueto avoid a particular road condition.

The inventors herein have recognized the above-mentioned disadvantagesand have developed a method of adjusting operation of a hybrid vehicle,comprising: adjusting a schedule for automatically stopping enginerotation in response to a condition of a driving surface.

By adjusting a schedule for automatically stopping an engine in responseto driving surface conditions, it may be possible to reduce an amount iftime between a request for additional wheel torque and the time torqueis actually delivered to vehicle wheels. In one example, an engine maybe allowed to idle decoupled from a vehicle driveline instead of comingto a complete stop when road conditions have degraded. Allowing theengine to idle avoids having to restart the engine. Consequently, torqueoutput from the engine may be made available to the vehicle driveline ina more timely manner.

The present description may provide several advantages. Specifically,the approach may reduce an amount of time it takes to provide a higherwheel torque. Further, the approach may improve vehicle drivability.Further still, the approach may reduce driveline wear, therebyincreasing the operating life of the driveline.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of an engine;

FIG. 2 shows a first example vehicle driveline configuration;

FIG. 3 shows a second example vehicle driveline configuration;

FIG. 4 is a first portion of a flowchart for controlling a driveline ofa hybrid vehicle;

FIG. 5 is a second portion of the flowchart for controlling thedriveline of the hybrid vehicle;

FIG. 6 is a third portion of the flowchart for controlling the drivelineof the hybrid vehicle;

FIG. 7 is a fourth portion of the flowchart for controlling thedriveline of the hybrid vehicle;

FIG. 8 is a fifth portion of the flowchart for controlling the drivelineof the hybrid vehicle;

FIG. 9 is a sixth portion of the flowchart for controlling the drivelineof the hybrid vehicle;

FIG. 10 is a seventh portion of the flowchart for controlling thedriveline of the hybrid vehicle;

FIG. 11 is a prophetic example sequence for operating a vehicle thatincludes a PTO;

FIG. 12 is a prophetic example sequence for operating a vehicle thatincludes a 4×4 low gear range mode; and

FIG. 13 is a prophetic example sequence for operating a vehicle inresponse to a driving surface.

DETAILED DESCRIPTION

The present description is related to controlling a driveline of ahybrid vehicle. The hybrid vehicle may include an engine and electricmachine as shown in FIGS. 1-3. The engine may be operated with orwithout a driveline integrated starter/generator (DISG) during vehicleoperation. The driveline integrated starter/generator is integrated intothe driveline on the same axis as the engine crankshaft and rotateswhenever the torque converter impeller rotates. Further, the DISG maynot be selectively engaged or disengaged with the driveline. Rather, theDISG is an integral part of the driveline. Further still, the DISG maybe operated with or without operating the engine. The mass and inertiaof the DISG remain with the driveline when the DISG is not operating toprovide or absorb torque from the driveline. The vehicle driveline maybe operated according to the method shown in FIGS. 4-10. FIGS. 11-13show example vehicle operating sequences according to the method shownin FIGS. 4-10.

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. Engine 10 includescombustion chamber 30 and cylinder walls 32 with piston 36 positionedtherein and connected to crankshaft 40. Flywheel 97 and ring gear 99 arecoupled to crankshaft 40. Starter 96 includes pinion shaft 98 and piniongear 95. Pinion shaft 98 may selectively advance pinion gear 95 toengage ring gear 99. Starter 96 may be directly mounted to the front ofthe engine or the rear of the engine. In some examples, starter 96 mayselectively supply torque to crankshaft 40 via a belt or chain. In oneexample, starter 96 is in a base state when not engaged to the enginecrankshaft. Combustion chamber 30 is shown communicating with intakemanifold 44 and exhaust manifold 48 via respective intake valve 52 andexhaust valve 54. Each intake and exhaust valve may be operated by anintake cam 51 and an exhaust cam 53. The position of intake cam 51 maybe determined by intake cam sensor 55. The position of exhaust cam 53may be determined by exhaust cam sensor 57.

Fuel injector 66 is shown positioned to inject fuel directly intocylinder 30, which is known to those skilled in the art as directinjection. Alternatively, fuel may be injected to an intake port, whichis known to those skilled in the art as port injection. Fuel injector 66delivers liquid fuel in proportion to the pulse width of signal FPW fromcontroller 12. Fuel is delivered to fuel injector 66 by a fuel system(not shown) including a fuel tank, fuel pump, and fuel rail (not shown).Fuel injector 66 is supplied operating current from driver 68 whichresponds to controller 12. In addition, intake manifold 44 is showncommunicating with optional electronic throttle 62 which adjusts aposition of throttle plate 64 to control air flow from air intake 42 tointake manifold 44. In one example, a low pressure direct injectionsystem may be used, where fuel pressure can be raised to approximately20-30 bar. Alternatively, a high pressure, dual stage, fuel system maybe used to generate higher fuel pressures. In some examples, throttle 62and throttle plate 64 may be positioned between intake valve 52 andintake manifold 44 such that throttle 62 is a port throttle.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of catalytic converter 70. Alternatively, atwo-state exhaust gas oxygen sensor may be substituted for UEGO sensor126.

Vehicle wheel brakes or regenerative braking via a DISG may be providedwhen brake pedal 150 is applied via foot 152. Brake pedal sensor 154supplies a signal indicative of brake pedal position to controller 12.Foot 152 is assisted by brake booster 140 applying vehicle brakes.

Converter 70 can include multiple catalyst bricks, in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 70 can be a three-way type catalyst inone example.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106, random access memory 108, keep alive memory 110, and aconventional data bus. Controller 12 is shown receiving various signalsfrom sensors coupled to engine 10, in addition to those signalspreviously discussed, including: engine coolant temperature (ECT) fromtemperature sensor 112 coupled to cooling sleeve 114; a position sensor134 coupled to an accelerator pedal 130 for sensing force applied byfoot 132; a measurement of engine manifold pressure (MAP) from pressuresensor 122 coupled to intake manifold 44; an engine position sensor froma Hall effect sensor 118 sensing crankshaft 40 position; a measurementof air mass entering the engine from sensor 120; and a measurement ofthrottle position from sensor 58. Barometric pressure may also be sensed(sensor not shown) for processing by controller 12. In a preferredaspect of the present description, engine position sensor 118 produces apredetermined number of equally spaced pulses every revolution of thecrankshaft from which engine speed (RPM) can be determined.

In some examples, the engine may be coupled to an electric motor/batterysystem in a hybrid vehicle as shown in FIGS. 2 and 3. Further, in someexamples, other engine configurations may be employed, for example adiesel engine.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into combustion chamber 30 via intake manifold 44, and piston36 moves to the bottom of the cylinder so as to increase the volumewithin combustion chamber 30. The position at which piston 36 is nearthe bottom of the cylinder and at the end of its stroke (e.g. whencombustion chamber 30 is at its largest volume) is typically referred toby those of skill in the art as bottom dead center (BDC). During thecompression stroke, intake valve 52 and exhaust valve 54 are closed.Piston 36 moves toward the cylinder head so as to compress the airwithin combustion chamber 30. The point at which piston 36 is at the endof its stroke and closest to the cylinder head (e.g. when combustionchamber 30 is at its smallest volume) is typically referred to by thoseof skill in the art as top dead center (TDC). In a process hereinafterreferred to as injection, fuel is introduced into the combustionchamber. In a process hereinafter referred to as ignition, the injectedfuel is ignited by known ignition means such as spark plug 92, resultingin combustion. During the expansion stroke, the expanding gases pushpiston 36 back to BDC. Crankshaft 40 converts piston movement into arotational torque of the rotary shaft. Finally, during the exhauststroke, the exhaust valve 54 opens to release the combusted air-fuelmixture to exhaust manifold 48 and the piston returns to TDC. Note thatthe above is shown merely as an example, and that intake and exhaustvalve opening and/or closing timings may vary, such as to providepositive or negative valve overlap, late intake valve closing, orvarious other examples.

FIG. 2 is a block diagram of a vehicle driveline 200. Driveline 200 maybe powered by engine 10. Engine 10 may be started with an enginestarting system shown in FIG. 1 or via DISG 240. Further, engine 10 maygenerate or adjust torque via torque actuator 204, such as a fuelinjector, throttle, etc.

An engine output torque may be transmitted to an input side of dual massflywheel 232. Engine speed as well as dual mass flywheel input sideposition and speed may be determined via engine position sensor 118.Dual mass flywheel 232 may include springs and separate masses (notshown) for dampening driveline torque disturbances. The output side ofdual mass flywheel 232 is shown being mechanically coupled to the inputside of disconnect clutch 236. Disconnect clutch 236 may be electricallyor hydraulically actuated. A position sensor 234 is positioned on thedisconnect clutch side of dual mass flywheel 232 to sense the outputposition and speed of the dual mass flywheel 232. The downstream side ofdisconnect clutch 236 is shown mechanically coupled to DISG input shaft237.

DISG 240 may be operated to provide torque to driveline 200 or toconvert driveline torque into electrical energy to be stored in electricenergy storage device 275. DISG 240 has a higher output power capacitythan starter 96 shown in FIG. 1. Further, DISG 240 directly drivesdriveline 200 or is directly driven by driveline 200. There are nobelts, gears, or chains to couple DISG 240 to driveline 200. Rather,DISG 240 rotates at the same rate as driveline 200. Electrical energystorage device 275 may be a battery, capacitor, or inductor. Thedownstream side of DISG 240 is mechanically coupled to the impeller 285of torque converter 206 via shaft 241. The upstream side of the DISG 240is mechanically coupled to the disconnect clutch 236. Torque converter206 includes a turbine 286 to output torque to input shaft 270. Inputshaft 270 mechanically couples torque converter 206 to automatictransmission 208. Torque converter 206 may include a power take off(PTO) 251 that can direct driveline torque to an external or ancillarymechanical load 252. The PTO 251 may be located on the impeller side ofthe torque converter or on the turbine side of the torque converter. Insome examples, the PTO may be included in the automatic transmission208. PTO 251 may also include a reverse gear 287.

Torque converter 206 also includes a torque converter bypass lock-upclutch 212 (TCC). Torque is directly transferred from impeller 285 toturbine 286 when TCC is locked. TCC is electrically operated bycontroller 12. Alternatively, TCC may be hydraulically locked. In oneexample, the torque converter may be referred to as a component of thetransmission. Torque converter turbine speed and position may bedetermined via position sensor 239. In some examples, 238 and/or 239 maybe torque sensors or may be combination position and torque sensors.

When torque converter lock-up clutch 212 is fully disengaged, torqueconverter 206 transmits engine torque to automatic transmission 208 viafluid transfer between the torque converter turbine 286 and torqueconverter impeller 285, thereby enabling torque multiplication. Incontrast, when torque converter lock-up clutch 212 is fully engaged, theengine output torque is directly transferred via the torque converterclutch to an input shaft 270 of transmission 208. Alternatively, thetorque converter lock-up clutch 212 may be partially engaged, therebyenabling the amount of torque directly relayed to the transmission to beadjusted. The controller 12 may be configured to adjust the amount oftorque transmitted by torque converter 212 by adjusting the torqueconverter lock-up clutch in response to various engine operatingconditions, or based on a driver-based engine operation request.

Mechanical load 252 may be a hydraulic pump that operates a snow plowlift or cement mixer. Alternatively, mechanical load 252 may be arotating mechanical device. Mechanical load controller 253 maycommunicate with controller 12 via communication link 291 to provideposition, speed, and torque information of mechanical load 252 viasensors 254. Sensors 254 provide position and speed information tomechanical load controller 253 which may in turn relay the informationto controller 12 so that the PTO may be controlled.

Automatic transmission 208 includes gear clutches (e.g., gears 1-6) 211and forward clutch 210. The gear clutches 211 and the forward clutch 210may be selectively engaged to propel a vehicle. Torque output from theautomatic transmission 208 may in turn be relayed to rear wheels 216 topropel the vehicle via output shaft 260. Specifically, automatictransmission 208 may transfer an input driving torque at the input shaft270 responsive to a vehicle traveling condition before transmitting anoutput driving torque to the rear wheels 216. Torque may also bedirected to front wheels 217 via transfer case 261.

Further, a frictional force may be applied to wheels 216 by engagingwheel brakes 218. In one example, wheel brakes 218 may be engaged inresponse to the driver pressing his foot on a brake pedal (not shown).In other examples, controller 12 or a controller linked to controller 12may apply engage wheel brakes. In the same way, a frictional force maybe reduced to wheels 216 by disengaging wheel brakes 218 in response tothe driver releasing his foot from a brake pedal. Further, vehiclebrakes may apply a frictional force to wheels 216 via controller 12 aspart of an automated engine stopping procedure.

A mechanical oil pump 214 may be in fluid communication with automatictransmission 208 to provide hydraulic pressure to engage variousclutches, such as forward clutch 210, gear clutches 211, and/or torqueconverter lock-up clutch 212. Mechanical oil pump 214 may be operated inaccordance with torque converter 206, and may be driven by the rotationof the engine or DISG via input shaft 241, for example. Thus, thehydraulic pressure generated in mechanical oil pump 214 may increase asan engine speed and/or DISG speed increases, and may decrease as anengine speed and/or DISG speed decreases.

Controller 12 may be configured to receive inputs from engine 10, asshown in more detail in FIG. 1, and accordingly control a torque outputof the engine and/or operation of the torque converter, transmission,DISG, clutches, and/or brakes. As one example, an engine torque outputmay be controlled by adjusting a combination of spark timing, fuel pulsewidth, fuel pulse timing, and/or air charge, by controlling throttleopening and/or valve timing, valve lift and boost for turbo- orsuper-charged engines. In the case of a diesel engine, controller 12 maycontrol the engine torque output by controlling a combination of fuelpulse width, fuel pulse timing, and air charge. In all cases, enginecontrol may be performed on a cylinder-by-cylinder basis to control theengine torque output. Controller 12 may also control torque output andelectrical energy production from DISG by adjusting current flowing toand from field and/or armature windings of DISG as is known in the art.Controller 12 also receives driving surface grade input information frominclinometer 281.

When idle-stop conditions are satisfied, controller 42 may initiateengine shutdown by shutting off fuel and spark to the engine. However,the engine may continue to rotate in some examples. Further, to maintainan amount of torsion in the transmission, the controller 12 may groundrotating elements of transmission 208 to a case 259 of the transmissionand thereby to the frame of the vehicle. In particular, the controller12 may engage one or more transmission clutches, such as forward clutch210, and lock the engaged transmission clutch(es) to the transmissioncase 259 and vehicle frame as described in U.S. patent application Ser.No. 12/833,788 “METHOD FOR CONTROLLING AN ENGINE THAT MAY BEAUTOMATICALLY STOPPED” which is hereby fully incorporated by referencefor all intents and purposes. A transmission clutch pressure may bevaried (e.g., increased) to adjust the engagement state of atransmission clutch, and provide a desired amount of transmissiontorsion.

A wheel brake pressure may also be adjusted during the engine shutdown,based on the transmission clutch pressure, to assist in tying up thetransmission while reducing a torque transferred through the wheels.Specifically, by applying the wheel brakes 218 while locking one or moreengaged transmission clutches, opposing forces may be applied ontransmission, and consequently on the driveline, thereby maintaining thetransmission gears in active engagement, and torsional potential energyin the transmission gear-train, without moving the wheels. In oneexample, the wheel brake pressure may be adjusted to coordinate theapplication of the wheel brakes with the locking of the engagedtransmission clutch during the engine shutdown. As such, by adjustingthe wheel brake pressure and the clutch pressure, the amount of torsionretained in the transmission when the engine is shutdown may beadjusted.

When restart conditions are satisfied, and/or a vehicle operator wantsto launch the vehicle, controller 12 may reactivate the engine byresuming cylinder combustion. As further elaborated with reference toFIGS. 4-9, the engine may be started in a variety of ways.

Referring now to FIG. 3, a second example vehicle drivelineconfiguration is shown. The elements in driveline 300 that have the samereference numbers as elements in FIG. 2 are equivalent elements andoperate as described in FIG. 2. Therefore, for the sake of brevity, thedescription of elements that are common between FIG. 2 and FIG. 3 isomitted. The description of FIG. 3 is limited to elements that aredifferent from the elements of FIG. 2.

Driveline 300 includes a dual clutch-dual layshaft transmission 308.Transmission 308 is essentially an automatically operated manualtransmission. Controller 12 operates first clutch 310, second clutch314, and shifting mechanism 315 to select between gears (e.g.,1^(st)-5^(th) gears) 317. First clutch 310 and second clutch 314 may beselectively opened and closed to shift between gears 317. Output shaft260 delivers torque from transmission 308 to wheels 216.

Referring now to FIG. 4, a flowchart of an example method forcontrolling a driveline of a hybrid vehicle is shown. The method of FIG.4 may be stored as executable instructions in non-transitory memory ofcontroller 12 shown in the systems of FIGS. 1-3.

At 401, method 400 determines vehicle operating conditions. Vehicleoperating conditions may include but are not limited to vehicle speed,brake pedal position, engine speed, engine load, 4×4 selection mode, 4×2selection mode, vehicle chassis information (e.g., wheel verticalmotion, yaw, pitch, and roll), and driving surface incline. Method 400proceeds to 402 after vehicle operating conditions are determined.

At 402, method 400 judges whether or not a PTO operation request hasbeen received. A PTO operation request may be made by a vehicle driveror an external controller communicating with powertrain controller 12shown in FIGS. 1-3. A PTO operation request indicates that it is desiredfor an external load to receive power from the engine 10 and/or electricmachine 240. If method 400 judges that a PTO operation request has beenmade, the answer is yes and method 400 proceeds to 412 of FIG. 5.Otherwise, the answer is no and method 400 proceeds to 403.

Referring now to FIG. 5, method 400 judges whether or not the PTOoperation request is for a stationary mode where the vehicle is parkedor in a non-stationary mode where the vehicle may move at 412.Stationary mode may be useful for external loads that are not requiredto move. In stationary mode, the PTO speed may be requested to be afixed speed (e.g., 540 RPM) input via control commands from an externalload device (e.g., a hydraulic pump controller) or a driver while thevehicle is stopped and/or parked. In non-stationary mode, the PTO speedmay vary with engine/motor speed and vehicle speed. Thus, torque may beprovided to the PTO and to provide motive force for the vehicle. Ifmethod 400 judges that stationary mode is requested, the answer is yesand method 400 proceeds to 413. Otherwise, the answer is no and method400 proceeds to 424.

At 413, method 400 judges whether DISG or electric machine only PTO modeis selected. In DISG only PTO mode, the PTO is supplied torque via onlythe DISG and not the engine. Such operation allows the PTO to operate inreverse and forward directions. If method 400 judges that DISG only PTOmode is selected the answer is yes and method 400 proceeds to 414.Otherwise, the answer is no and method 400 proceeds to 434 of FIG. 6.

At 434, method 400 closes the driveline disconnect clutch so that theengine and DISG are mechanically coupled together. The engine or theDISG may be selectively deactivated while the driveline disconnectclutch is closed. Method 400 proceeds to 435 after the disconnect clutchis closed.

At 435, method 400 judges whether or not engine output is above oralternatively within a threshold torque range of a threshold torquelevel. If engine output torque is within or above a threshold torque,the answer is yes and method 400 proceeds to 437. Otherwise, the answeris no and method 400 proceeds to 436. For example, if engine torque is100 N-m, the threshold torque range is 10 N-m, and the threshold torqueis 108 N-m, then the answer is yes and method 400 proceeds to 437.

At 437, method 400 adjusts engine torque and DISG torque to provide thedesired PTO speed. In one example, engine load is adjusted to athreshold level (e.g., 90 percent of maximum engine torque) and thenDISG output torque is increased to a level where the desired PTO speedis provided. If the DISG output torque is at a maximum level and PTOspeed is less than desired PTO speed, engine torque may be increased toa maximum level at the present PTO speed. Method 400 proceeds to 404 ofFIG. 4 after engine and DISG torque are adjusted.

In other examples, while battery state of charge is greater than athreshold level, the DISG may output torque to a threshold level beforethe engine is activated. Further, the engine may charge vehiclebatteries and provide electrical power to the vehicle's electric networkwhile the PTO is in a stationary mode and PTO torque requirements areless than available engine output torque. Thus, the engine may drive thePTO load while the DISG converts engine torque to electricity to chargethe vehicle batteries.

At 436, method 400 adjusts engine torque to provide the desired PTOspeed while the DISG is deactivated. Alternatively, the DISG may be in agenerating mode supplying current to vehicle batteries at 436. The PTOspeed may be maintained by controller 12 which determines an errorbetween desired PTO speed and actual PTO speed. If actual PTO speed isless than desired PTO speed, the engine throttle may be opened furtherto increase engine torque, thereby increasing PTO speed. If actual PTOspeed is greater than desired PTO speed, the engine torque may bedecreased via at least one of a plurality of actuators (e.g., throttle,cam timing, waste gate, fuel injectors, spark timing, etc.), therebyreducing PTO speed. Method 400 proceeds to 404 of FIG. 4 after enginetorque is adjusted.

Returning now to FIG. 5, method 400 judges whether or not battery stateof charge (SOC) is greater than a threshold charge level at 414. In oneexample, the threshold state of charge may be estimated via measuringbattery voltage. If battery charge is greater than a threshold level,the answer is yes and method 400 proceeds to 417. Otherwise, the answeris no and method 400 proceeds to 415. In one example, the thresholdstate of charge is a minimum charge level where battery degradation doesnot occur.

At 415, method 400 indicates an impending DISG shutdown. A DISG shutdownmay be indicated via a light, display panel, or audible actuator. Theindication of an impending shutdown may be provided at a battery stateof charge that is above the threshold charge level mentioned at 414.Alternatively, the engine may be automatically started when the batterycharge is reduced to the threshold level and the PTO continues tooperate.

At 416, method 400 ceases to provide torque to the PTO via the DISG. TheDISG torque may be ramped down in a controlled manner so as to avoid arapid change in PTO torque. Method 400 proceeds to 404 of FIG. 4.

At 417, method 400 opens the driveline disconnect clutch. Opening thedriveline disconnect clutch mechanically decouples the engine from theDISG. Thus, the DISG can supply torque to the PTO without having lossesdue to rotating an engine that is not combusting air-fuel mixtures.Since the PTO is in stationary mode, most of the torque provided by theDISG is transferred to the PTO. Method 400 proceeds to 418 after thedisconnect clutch is opened.

At 418, method 400 exchanges control signals with a mechanical loadcontroller (e.g., 253 of FIG. 2). The mechanical load controller maycontrol the PTO and the engine to provide a desired PTO output.Alternatively, the mechanical load controller may receive instructionsfrom the powertrain controller and provide control signals from sensorsto the powertrain controller. Example signals exchanged between themechanical load controller and the powertrain controller include but arenot limited to PTO speed, PTO device position (e.g., a position of anactuator such as a ball screw), PTO engage signal, PTO disengage signal,PTO device end of travel, PTO rotation direction, and PTO stop signal.Method 400 proceeds to 419 after signals are exchanged between themechanical load controller and the powertrain controller.

At 419, method 400 judges whether or not reverse PTO rotation isrequested. Reverse PTO rotation may be requested by an operator or acontroller such as the mechanical load controller. If method 400 judgesthat a request for reverse rotation is present, the answer is yes andmethod 400 proceeds to 420. If method 400 judges that a request forreverse rotation is not present, the answer is no, the PTO rotates in aforward direction, and method 400 proceeds to 421.

At 420, the DISG is rotated so that the PTO rotates in a reversedirection. Reverse DISG rotation may be provided via a reverse gear thatis incorporated into the PTO device. The reverse gear may be selectivelyengaged. Alternatively, the DISG may be rotated in a reverse directionso that the PTO rotates in a reverse direction without a reverse gear.Reverse DISG rotation may be provided via electric commutation oralternatively in some configurations by reversing polarity of powerapplied to the DISG.

At 421, method 400 operates the DISG and PTO at the desired speed. Inone example, the DISG speed is controlled according to the actual PTOspeed. For example, the actual PTO speed may be subtracted from thedesired PTO speed to provide a PTO speed error. The current supplied tothe DISG may then be adjusted to adjust the DISG torque so as to providezero error between the actual PTO speed and the desired PTO speed. Ifactual PTO speed is less than desired PTO speed, the DISG current may beincreased. Alternatively, depending on the DISG design, the frequency ofpower supplied to the DISG may be adjusted to adjust the DISG torque.Method 400 proceeds to 422 after DISG speed is adjusted to provide thedesired PTO speed.

At 422, method 400 judges whether or not a PTO operated device is at alimit. In one example, the PTO operated device may be a ball screw withstart of travel and end of travel limit switches. If the PTO operateddevice is at a travel limit the answer is yes and method 400 proceeds to423. Otherwise, the answer is no and method 400 proceeds to 404 of FIG.4.

At 423, method 400 stops DISG and PTO rotation. DISG and PTO rotationmay be ramped down at a predetermined rate once the PTO operated devicereaches a limit condition. The DISG may be restarted in an oppositedirection via an operator or controller input. In this way, the DISG maybe operated with the PTO such that the PTO operated device moves betweentwo limit positions. Method 400 proceeds to 404 of FIG. 4 after DISGrotation is ceased.

At 424, method judges whether or not battery state of charge is greaterthan a threshold state of charge. If battery state of charge is greaterthan the threshold level, the answer is yes and method 400 proceeds to427. Otherwise, the answer is no and method 400 proceeds to 425. Thethreshold state of charge helps to ensure that the DISG may be suppliedenough power to continue rotating the PTO.

At 425, method 400 activates the engine if the engine is stopped. Theengine may be activated by starting the engine. In one example, theengine may be started via supplying air, spark, and fuel to the enginewhile the disconnect clutch is engaged with the DISG rotating. Method400 proceeds to 426 after the engine is activated.

At 426, method 400 stops providing positive torque (e.g., torque torotate the driveline) via the DISG. However, the DISG may provideelectrical energy to vehicle batteries via transforming drivelinerotational energy into electrical energy. Method 400 proceeds to 427after DISG positive output torque has been reduced.

At 427, method 400 judges whether or not the DISG can provide thedesired amount of wheel torque plus an additional predetermined amountof torque to rotate the PTO. In one example, 25% of the available DISGtorque is reserved for PTO operation. For example, if the DISG has atorque output capacity of 100 N-m at speeds below its base speed, 75 N-mof DISG torque can be provided to produce wheel torque. The remaining 25N-m is reserved for providing PTO torque. However, if the desired wheeltorque is low, the PTO may receive up to 75% of the available DISGoutput torque. The desired wheel torque may be determined by inputtingaccelerator pedal position into a look up function or table thatconverts pedal position into desired impeller, turbine, transmissionoutput or wheel torque. The desired torque is then compared to torquethat is available via the DISG. The available DISG torque may be storedin memory in a lookup table that is indexed via battery state of chargeand DISG speed. If the available DISG torque is greater than the DISGtorque that produces the desired torque, the answer is yes and method400 proceeds to 432. Otherwise, the answer is no and method 400 proceedsto 428. Note that the desired torque may be converted into a desiredDISG torque by accounting for transmission gear ratios and transmissionlosses, as appropriate depending on the form of desired torque.

At 428, method 400 closes the disconnect clutch. The disconnect clutchis closed so that torque provided by the DISG may be augmented by enginetorque. Further, the engine is started if it is not already running. Inthis way, torque provided by the DISG may be combined with engine torqueto provide the desired wheel torque while the PTO in operating and thevehicle is moving. Method 400 proceeds to 429 after the disconnectclutch is closed and the engine is started.

At 429, method 400 judges whether or not the engine alone, without theDISG providing positive torque to the driveline, has torque capacity toprovide the desired wheel torque plus an additional predetermined amountof torque to rotate the PTO. In one example, the desired wheel torquemay be converted into a desired engine torque via accounting fortransmission gearing and losses. In one example, 25% of the availableengine torque is reserved for PTO operation. For example, if the enginehas a torque output capacity of 200 N-m at a particular speed, 150 N-mof engine torque can be provided to produce wheel torque. The remaining50 N-m is reserved for providing PTO torque. However, if the desiredwheel torque is low, the PTO may receive up to 75% of the availableengine output torque. In one example, the desired wheel torque iscompared to torque that is available via the engine. The availableengine torque may be stored in memory in a lookup table that is indexedvia engine speed and adjusted for ambient air density or calculatedreal-time based on a model of the maximum engine torque at currentconditions and hardware capability. If the available engine torque isgreater than the engine torque that produces the desired wheel torque,the answer is yes and method 400 proceeds to 430. Otherwise, the answeris no and method 400 proceeds to 431. Note that the desired wheel torquemay be converted into a desired engine torque by accounting fortransmission gear ratios and transmission losses.

At 430, method 400 adjusts engine torque to provide desired wheel torquewhile the PTO is driving an external device. Since the amount of enginetorque transferred to the PTO may not be known in some examples, thetorque provided to the PTO may be determined and added to the desiredengine torque so that the desired wheel torque is provided. In oneexample, torque provided to the PTO may be determined from the equation:T _(Pto) =T _(eng) −Tc _(mult) ·T _(gear) _(_) _(ratio) ·T _(axle) _(_)_(ratio) ·T _(driveline) _(_) _(losses) ·F _(Grade)where T_(wheel) is desired wheel torque, T_(eng) is desired enginetorque, T_(pto) is PTO torque, Tc_(mult) is the torque convertermultiplication ratio, T_(gear) _(_) _(ratio) is the current transmissiongear ratio, T_(axle) _(_) _(ratio) is the axle ratio, T_(driveline) _(_)_(losses) is a multiplier that reflects driveline losses, and F_(Grade)is a grade multiplier that accounts for road grade determined via theinclinometer. The desired engine torque may be estimated via a map ofengine torque that is indexed by engine speed and load. The wheel torquemay be estimated from the equation:T _(wheel)=(T _(eng) −T _(pto))·Tc _(mult) ·T _(gear) _(_) _(ratio) ·T_(axle) _(_) _(ratio) ·T _(driveline) _(_) _(losses) ·F _(Grade)The torque converter torque multiplication ratio, the gear ratio, axleratio, and driveline torque loss multiplier may be empiricallydetermined and retrieved from memory based on engine speed, vehiclespeed, selected gear ratio, and other factors. The vehicle inertia maybe adjusted for varying vehicle mass.

If the estimated wheel torque is less than desired, the desired enginetorque may be increased via adjusting engine torque to increase theactual wheel torque to the desired wheel torque. In this way, enginetorque may be increased to provide the desired wheel torque even thoughthe amount of torque consumed by the PTO is unknown. Method 400 proceedsto 404 of FIG. 4.

At 431, method 400 adjusts engine torque and DISG torque to provide thedesired wheel torque while the PTO is driving an external device. In oneexample, the engine is operated at an efficient operating conditionbased on vehicle speed and the selected transmission gear. If thedesired wheel torque is not available at the operating condition, DISGoutput torque is increased to provide the desired wheel torque. If theDISG does not have the capacity to provide the desired wheel torque inthe presence of a PTO load, the engine operation is adjusted to increaseengine torque output at a lower fuel efficiency operating condition.DISG torque is increased via increasing current supplied to the DISG.Engine torque is adjusted via adjusting throttle position, waste gateposition, cam timing, fuel amount, and spark timing. In one example, thewheel torque may be determined according to the following equation whenthe DISG is providing torque to the driveline:T _(wheel)=(T _(eng) −T _(pto) +T _(DISG))·Tc _(mult) ·T _(gear) _(_)_(ratio) ·T _(axle) _(_) _(ratio) ·T _(driveline) _(_) _(losses) ·F_(Grade)where T_(DISG) is the amount of torque provided to the driveline via theDISG and where the remaining variables are as described above. Thus, theengine torque and the DISG torque can be adjusted to provide the desiredwheel torque in the presence of a PTO load. Method 400 proceeds to 404of FIG. 4 after the engine torque and DISG torque are adjusted.

At 432, the disconnect clutch is opened and the engine is stopped. Thedisconnect clutch is opened so that the DISG does not have to rotate thedeactivated engine. The engine is deactivated to conserve fuel. Method400 proceeds to 433 after the disconnect clutch is opened.

At 433, method 400 adjusts DISG torque via adjusting current supplied tothe DISG. In one example, the DISG torque is adjusted to provide thedesired wheel torque while the PTO is passively operated. For example,if 15 N-m of wheel torque is desired and the PTO is consuming 5 N-m, theDISG torque is adjusted to 20 N-m by increasing DISG torque until thevehicle accelerates at a rate expected when there is 15 N-m of wheeltorque.

Returning now to FIG. 4, method 400 recharges the batteries via the DISGtransforming rotational energy from the engine or kinetic vehicle energyinto electrical energy at 403. In some examples, battery charging may bedelayed after PTO operation until the vehicle is in a decelerationcondition or traveling down a hill where the vehicle's kinetic energycan be converted to electrical energy without combusting an air-fuelmixture to provide the electrical energy. In other examples, thebatteries may be charged to a threshold level via converting enginerotational energy into electrical energy. Once the batteries reach thethreshold level, any additional battery charging may originate solelyfrom vehicle kinetic energy. Method 400 proceeds to 404 after batterycharging is initiated.

At 404, method 400 judges whether or not there is a request for 4×4 mode(e.g., four wheel drive mode). A request for 4×4 mode may be made by adriver or an external controller (e.g., a controller that senses wheelslip). If method 400 judges that a request for 4×4 mode is present, theanswer is yes and method 400 proceeds to 407. Otherwise, the answer isno and method 400 proceeds to 405. In some examples, method 400automatically starts a stopped engine when the driver selects a fourwheel high or low gear range while the vehicle is in a two wheel drivemode.

At 405, method 400 judges whether or not degraded (e.g., rough, curvy(frequency of road turns), slick, or obstructed) road conditions arepresent. In one example, a rough road may be determined based on avertical travel distance and frequency of vertical motion of vehiclewheels. Slick roads may be determined by an amount of wheel slippage. Anobject obstructing a road in front of the vehicle may be detected via anoptical, sonic, or radar sensing device. If a rough, curvy, slick, orobstructed road is present, the answer is yes and method 400 proceeds to450 of FIG. 7. Otherwise, the answer is no and method 400 proceeds to406.

At 406, method 400 operates the engine and driveline disconnect clutchaccording to base two wheel drive automated modes. During two wheeldrive modes, the DISG may be selectively coupled to the engine via thevehicle disconnect clutch to provide wheel torque and to charge vehiclebatteries and provide electrical power to the vehicle's electricnetwork. In one example, the DISG provides torque to the vehicledriveline during vehicle acceleration while battery SOC is above athreshold SOC. Further, the DISG provides electrical energy to vehiclebatteries during vehicle deceleration and during hill decent conditions.Method 400 returns to 401 after the engine and DISG are operatedaccording to base two wheel drive mode conditions.

Referring now to FIG. 7, method 400 judges whether or not closing rate(e.g., a rate the vehicle approaches an object) is faster (e.g., ashorter time between contact between the vehicle and the object) than afirst threshold closing rate or if a degraded road condition (e.g.,curvy, slick, or rough road condition) metric (e.g., a numberrepresenting a curvy, slick, or rough road condition) is greater than afirst threshold road condition metric amount at 450. In other words,method 400 judges whether or not a higher level of road roughness,curviness, slickness, or a high rate of closing to an object is present.If method 400 judges that a road condition metric is greater than afirst threshold road condition parameter, or if the vehicle closing rateis faster than a first vehicle threshold closing rate, the answer is yesand method 400 proceeds to 451. Otherwise, the answer is no and method400 proceeds to 454.

At 451, method 400 ceases automatic engine stopping and engine idlereadiness mode. Engine idle readiness mode is a mode where the engine isallowed to idle with the driveline disconnect clutch in an open stateand while the DISG provides torque to the driveline. For example, method400 may prevent automatic engine stopping during vehicle deceleration orwhen the vehicle is stopped. Automatic engine stopping is an engine stopthat is initiated by a controller based on inputs without a specificengine stop request provided by a driver input that has a sole purposeof stopping and/or starting the engine. By ceasing automatic enginestopping, the powertrain may be in a state that is better suited toresponding to road and vehicle conditions. For example, full powertraintorque (e.g., via the engine and DISG) is available so that the vehiclemay overcome or accelerate away from undesirable conditions. Further,the driveline disconnect clutch is closed or held closed at 451 so thatthe engine and DISG rotate at a same rate. Method 400 proceeds to 452after automatic engine rotation stopping is ceased.

At 452, method 400 judges whether or not the engine has presentlystopped rotating. The engine may be judged to be stopped rotating whenengine rotational speed is zero. If method 400 judges that the engine isstopped rotating, the answer is yes and method 400 proceeds to 453.Otherwise, the answer is no and method 400 proceeds to 454.

At 453, method 400 restarts the engine to ready it for any action thedriver may take. The engine may be started rotating via closing thedriveline disconnect clutch and supplying spark and fuel to the engine.Method 400 proceeds to 454 after the engine is restarted.

At 454, method 400 judges whether or not closing rate is slower than thefirst threshold closing rate and faster than a second threshold closingrate, or if a road condition (e.g., a slick or rough road condition)metric is less than the first threshold road condition parameter andgreater than a second threshold road condition parameter. The secondthreshold closing rate is lower than the first threshold closing rate.The second threshold road condition is lower than the first thresholdroad conditions. In other words, method 400 judges whether or not amid-higher level of road roughness, curviness, slickness, or a mid-highrate of closing to an object is present. If method 400 judges that theroad condition is less than the first threshold road condition andgreater than the second threshold road condition, or if the vehicleclosing is less than the first vehicle threshold closing rate andgreater than the second vehicle threshold closing rate, the answer isyes and method 400 proceeds to 455. Otherwise, the answer is no andmethod 400 proceeds to 458.

At 455, method 400 allows automatic engine output reduction to engineidle readiness mode via opening the driveline disconnect clutch duringlow wheel torque request conditions, but automatic stopping of enginerotation is not allowed. For example, at low desired wheel torques, theengine can be decoupled from the DISG, and then the engine speed isreduced to an idle speed. Torque may be provided to the driveline viathe DISG. If the wheel torque demand increases, the engine speed isincreased to DISG speed, and then the driveline disconnect clutch isclosed. In this way, method 400 increases the vehicle's state ofreadiness during some conditions but allows fuel to be conserved byallowing the engine to idle rather than rotating synchronously with theDISG when the vehicle is in 4×2 operating mode. Method 400 proceeds to456 after automatic stopping conditions are revised.

At 456, method 400 judges whether or not the engine is presently stoppedrotating. The engine may be judged to be stopped rotating when enginerotational speed is zero. If method 400 judges that the engine rotationis stopped, the answer is yes and method 400 proceeds to 457. Otherwise,the answer is no and method 400 proceeds to 458.

At 457, method 400 restarts the engine to ready it for any action thedriver may take. The engine may be started via closing the drivelinedisconnect clutch and supplying spark and fuel to the engine. Method 400proceeds to 458 after the engine is restarted.

At 458, method 400 judges whether or not a closing rate is slower thanthe second threshold closing rate and faster than a third thresholdclosing rate, or if a road condition metric (e.g., a slick or rough roadcondition) is less than the second threshold road condition parameterand greater than a third threshold road condition parameter. The thirdthreshold closing rate is slower (e.g., a longer time period betweencontact between the vehicle and the object) than the second thresholdclosing rate. The third threshold road condition parameter is lower thanthe second threshold road condition parameter. In other words, method400 judges whether or not a middle level of road roughness, curviness,slickness, or a middle rate of closing to an object is present. Ifmethod 400 judges that a road condition metric is less than the secondthreshold road condition parameter and greater than the third thresholdroad condition parameter, or if the vehicle closing is slower than thesecond vehicle threshold closing rate and faster than the third vehiclethreshold closing rate, the answer is yes and method 400 proceeds to459. Otherwise, the answer is no and method 400 proceeds to 464 of FIG.8.

At 459, method 400 allows automatic engine stopping rotation to zeroengine speed. The engine speed may be reduced to zero when the vehiclewheel torque demand is low by opening the driveline disconnect clutchand ceasing fuel flow to the engine. The DISG may continue to providetorque to the vehicle driveline to propel the vehicle. In this way,method 400 allows further reduction in fuel consumption when the vehicleis in a two wheel drive mode rather than a four wheel drive mode. Method400 proceeds to 464 of FIG. 8 after automatic engine stopping conditionsare revised.

It should be noted that method 400 may substitute a closing distanceless than a first, second, or third threshold for the closing rategreater than a first, second, or third threshold at 440, 444, 448, 450,454 and 458 if desired. Alternatively, method 400 may judge whether ornot a closing rate is greater than a first, second, or third threshold,and whether a closing distance is less than a first, second, or thirdthreshold at 440, 444, 448, 450, 454, and 458.

Referring now to FIG. 8, it is judged whether or not a closing rate isslower than the third threshold closing rate or if a road conditionmetric (e.g., a number representing a curvy, slick, or rough roadcondition) is less than the third threshold road condition parameter at464. In other words, method 400 judges whether or not a lower level ofroad roughness, curviness, slickness, or a lower rate of closing to anobject is present. If method 400 judges that a road condition metric isless than the third threshold road condition parameter, or if thevehicle closing is slower than the third vehicle threshold closing rateparameter, the answer is yes and method 400 proceeds to 465. Otherwise,the answer is no and method 400 returns to 401 of FIG. 4.

At 465, method 400 allows automatic engine stopping rotation to zeroengine speed. The engine speed may be reduced to zero when the vehiclewheel torque demand is low by opening the driveline disconnect clutchand ceasing fuel flow to the engine. If the wheel torque demandincreases, the engine may be restarted via the DISG or a starter and thedriveline disconnect clutch may be closed so that driveline and wheeltorque is increased. The DISG may continue to provide torque to thevehicle driveline to propel the vehicle while decoupled from the engine.Method 400 returns to 401 of FIG. 4 after automatic engine stoppingconditions are revised.

Referring now to FIG. 4, at 407 method 400 judges whether or notdegraded (e.g., rough, curvy, slick, or obstructed) road conditions arepresent. Road conditions and obstructions may be determined as describedat 405. If a rough, curvy, slick, or obstructed road is present, theanswer is yes and method 400 proceeds to 440 of FIG. 7. Otherwise, theanswer is no and method 400 proceeds to 408.

Referring now to FIG. 7, method 400 judges whether or not closing rate(e.g., a rate the vehicle approaches an object) is faster (e.g., ashorter time between contact between the vehicle and the object) than afirst threshold closing rate or if a road condition (e.g., curvy, slick,or rough road condition) metric is greater than a first threshold roadcondition metric amount at 440. In other words, method 400 judgeswhether or not a higher level of road roughness, curviness, slickness,or a high rate of closing to an object is present. If method 400 judgesthat a road condition metric is greater than a first threshold roadcondition parameter, or if the vehicle closing rate is faster than afirst vehicle threshold closing rate, the answer is yes and method 400proceeds to 441. Otherwise, the answer is no and method 400 proceeds to444.

The first through third threshold road conditions mentioned between 440and 448 may be the same or different than the first through thirdthreshold road conditions mentioned between 450 and 458. Similarly, thefirst through third threshold closing rates mentioned between 440 and448 may be the same or different than the first through third thresholdclosing rates mentioned between 450 and 458.

At 441, method 400 ceases automatic engine stopping. For example, method400 prevents automatic engine stopping during vehicle deceleration orwhen the vehicle is stopped. Automatic engine stopping is an engine stopthat is initiated by a controller based on inputs without a specificengine stop request provided by a driver input that has a sole purposeof stopping and/or starting the engine. By ceasing automatic enginestopping, the powertrain may be in a state that is better suited toresponding to road and vehicle conditions. For example, full powertraintorque (e.g., via the engine and DISG) is available so that the vehiclemay overcome or accelerate away from undesirable conditions. Further,the driveline disconnect clutch is closed or held closed at 441 so thatthe engine and DISG rotate at a same rate. Method 400 proceeds to 442after automatic engine rotation stopping is ceased.

At 442, method 400 judges whether or not the engine has presentlystopped rotating. The engine may be judged to be stopped rotating whenengine rotational speed is zero. If method 400 judges that the engine isstopped rotating, the answer is yes and method 400 proceeds to 443.Otherwise, the answer is no and method 400 proceeds to 444.

At 443, method 400 restarts the engine rotating to ready it for anyaction the driver may take. The engine may be started rotating viaclosing the driveline disconnect clutch and supplying spark and fuel tothe engine. Method 400 proceeds to 444 after the engine is restarted.

At 444, method 400 judges whether or not closing rate is slower than thefirst threshold closing rate and faster than a second threshold closingrate, or if a road condition (e.g., a slick, curvy, or rough roadcondition) metric is less than the first threshold road conditionparameter and greater than a second threshold road condition parameter.The second threshold closing rate is lower than the first thresholdclosing rate. The second threshold road condition is lower than thefirst threshold road conditions. In other words, method 400 judgeswhether or not a mid-higher level of road roughness, curviness,slickness, or a mid-high rate of closing to an object is present. Ifmethod 400 judges that the road condition is less than the firstthreshold road condition and greater than the second threshold roadcondition, or if the vehicle closing is less than the first vehiclethreshold closing rate and greater than the second vehicle thresholdclosing rate, the answer is yes and method 400 proceeds to 445.Otherwise, the answer is no and method 400 proceeds to 448.

At 445, method 400 allows automatic engine output reduction to engineidle conditions via opening the driveline disconnect clutch during lowwheel torque request conditions, but automatic stopping of enginerotation is not allowed. For example, at low desired wheel torques, theengine can be decoupled from the DISG, and then the engine speed isreduced to an idle speed. Torque may be provided to the driveline viathe DISG. If the wheel torque demand increases, the engine speed isincreased to DISG speed, and then the driveline disconnect clutch isclosed. In this way, method 400 increases the vehicle's state ofreadiness during some conditions but allows fuel to be conserved byallowing the engine to idle rather than rotating synchronously with theDISG when the vehicle is in 4×4 operating mode. Method 400 proceeds to446 after automatic stopping conditions are revised.

At 446, method 400 judges whether or not the engine is presently stoppedrotating. The engine may be judged to be stopped rotating when enginerotational speed is zero. If method 400 judges that the engine rotationis stopped, the answer is yes and method 400 proceeds to 447. Otherwise,the answer is no and method 400 proceeds to 448.

At 447, method 400 restarts the engine to ready it for any action thedriver may take. The engine may be started via closing the drivelinedisconnect clutch and supplying spark and fuel to the engine. Method 400proceeds to 448 after the engine is restarted.

At 448, method 400 judges whether or not closing rate is slower than thesecond threshold closing rate and faster than a third threshold closingrate, or if a road condition metric (e.g., a slick or rough roadcondition) is less than the second threshold road condition parameterand greater than a third threshold road condition parameter. The thirdthreshold closing rate is slower (e.g., a longer time period betweencontact between the vehicle and the object) than the second thresholdclosing rate. The third threshold road condition parameter is lower thanthe second threshold road condition parameter. In other words, method400 judges whether or not a middle level of road roughness, curviness,slickness, or a middle rate of closing to an object is present. Ifmethod 400 judges that a road condition metric is less than the secondthreshold road condition parameter and greater than the third thresholdroad condition parameter, or if the vehicle closing is slower than thesecond vehicle threshold closing rate and faster than the third vehiclethreshold closing rate, the answer is yes and method 400 proceeds to449. Otherwise, the answer is no and method 400 proceeds to 460 of FIG.8.

At 449, method 400 allows automatic engine output reduction to engineidle conditions via opening the driveline disconnect clutch during lowwheel torque request conditions, but automatic stopping of enginerotation is not allowed. Thus, the driveline's state of readiness torespond to varying driver wheel torque commands that may be influencedby vehicle and road conditions is higher in four wheel drive mode ascompared to when the vehicle is operated in two wheel drive mode. Method400 proceeds to 460 of FIG. 8 after automatic engine stopping conditionsare revised.

Referring now to FIG. 8, it is judged whether or not engine rotation hasstopped. If so, the answer is yes and method 400 proceeds to 461. Ifnot, the answer is no and method 400 proceeds to 461.

At 461, the engine is restarted. The engine may be restarted viasupplying spark and fuel to the engine and cranking the engine using theDISG or a separate starter. Method 400 proceeds to 462 after the engineis started.

At 462, it is judged whether a closing rate of the vehicle to an objectis slower than the third threshold closing rate or if a road conditionmetric is less than the third threshold road condition parameter. Inother words, method 400 judges whether or not a lower level of roadroughness, curviness, slickness, or a lower rate of closing to an objectis present. If method 400 judges that a road condition metric is lessthan the third threshold road condition parameter, or if the vehicleclosing is slower than the third vehicle threshold closing rateparameter, the answer is yes and method 400 proceeds to 463. Otherwise,the answer is no and method 400 returns to 408 of FIG. 4.

At 463, method 400 allows automatic engine stopping rotation to zeroengine speed. The engine speed may be reduced to zero when the vehiclewheel torque demand is low by opening the driveline disconnect clutchand ceasing fuel flow to the engine. If the wheel torque demandincreases, the engine may be restarted via the DISG or a starter and thedriveline disconnect clutch may be closed so that driveline and wheeltorque is increased. The DISG may continue to provide torque to thevehicle driveline to propel the vehicle while decoupled from the engine.Method 400 returns to 408 of FIG. 4 after automatic engine stoppingconditions are revised.

Returning now to FIG. 4, it is judged whether or not a request for fourwheel drive low (4×4 low) mode is requested at 408. Four wheel drive lowmode may be selected by a driver or by a controller. If method 400judges that four wheel drive low mode is selected, the answer is yes andmethod 400 proceeds to 466 of FIG. 9. Otherwise, the answer is no andmethod 400 proceeds to 409.

Referring now to FIG. 9, method 400 adjusts engine starting conditionsto include restarting an engine that has stopped rotating upon a driveror controller releasing a brake pedal or actuator. Further, thedisconnect clutch is closed so that engine torque is provided to vehiclewheels. Thus, when the driveline is in four wheel drive low range, theengine may be automatically started without a specific request by adriver to restart the engine via a dedicated input that has a solefunction of starting and/or stopping the engine. Starting the engineupon brake release allows the drivetrain to increase wheel torque ascompared to when only the DISG is providing torque to vehicle wheels.Method 400 proceeds to 467 after engine restarting conditions areadjusted to restart the engine upon release of a brake.

At 467, method 400 commands torque converter input command torqueresponsive to a schedule that is different than when the vehicle isoperated in a four wheel drive high range or a two wheel drive mode. Forexample, the DISG and engine may contribute different amounts of torqueto the torque converter impeller while the vehicle is operated in fourwheel drive low range as compared to when the vehicle is operated in twowheel drive or four wheel high range. In particular, during four wheeldrive low range, the DISG may provide a higher percentage of wheeltorque than the engine when desired wheel torque is less than athreshold torque so that the vehicle may accelerate more smoothly. Incontrast, during four wheel drive high range, the engine may provide ahigher percentage of wheel torque than the DISG when desired wheeltorque is less than the same threshold torque.

Additionally, the engine may be started and stopped automaticallywithout input from a driver operating a dedicated input that has a solepurpose of starting and/or stopping engine rotation at differentoperating conditions when the vehicle is operated in four wheel drivelow mode as compared to when the vehicle is operated in two wheel driveor in four wheel drive high range. For example, the engine may continueto idle for a longer period of time after the vehicle stops moving whilein four wheel low mode as compared to when the vehicle is operated intwo wheel drive mode or four wheel drive high gear range. Method 400proceeds to 468 after torque converter input torque scheduling andengine running scheduling are adjusted for four wheel drive low range.

At 468, method 400 commands a unique battery state of charge thresholdat which the engine may be automatically stopped while the vehicle isoperated in a four wheel drive low range. In one example, the engine maybe stopped after battery state of charge has reached a first batterycharge threshold while the vehicle is operated in four wheel drive lowrange. On the other hand, the engine may be stopped after battery stateof charge has reached a second battery charge threshold, the secondbattery charge threshold lower than the first battery charge threshold,when the vehicle is operated in two wheel drive or four wheel drive highrange. The engine may be automatically stopped after battery state ofcharge reaches a higher level while the vehicle is in four wheel drivelow range so that the number of times the disconnect clutch is engagedand disengaged may be mitigated to reduce disconnect clutch degradation.When the vehicle is not operated in the four wheel drivel low gearrange, engine rotation may be stopped at a lower state of battery chargeso that less fuel may be consumed to charge the batteries.

Further, the driveline disconnect clutch may be closed and openedaccording to a different schedule at 468 as compared to when the vehicleis operated in a four wheel drive low range as compared to when thevehicle is operated in a four wheel drive high range or in a two wheeldrive mode. In one example, the driveline disconnect clutch is held in aclosed state when the vehicle is operated in a four wheel drive lowrange while the driveline disconnect clutch may be selectively openedwhen the vehicle is operated in four wheel drive high range and duringtwo wheel drive. In another example, the driveline disconnect clutch maybe opened after the vehicle has been stopped for a first amount of timewhile the vehicle is operated in four wheel drive low range. Incontrast, the driveline disconnect clutch may be opened after thevehicle has been stopped for a second amount of time, the second amountof time less than the first amount of time, while the vehicle isoperated in two wheel drive or four wheel drive high range. Method 400proceeds to 410 of FIG. 4 after disconnect clutch and automatic enginestopping schedules are adjusted for four wheel drive low range.

Returning now to FIG. 4, at 409, method 400 allows the DISG to propelthe vehicle without starting the engine upon releasing the vehiclebrake. Further, the DISG may propel the vehicle up to a threshold wheeltorque demand and/or until battery SOC is reduced to a threshold level.By propelling the vehicle with the DISG and without the engine, it ispossible to allow the vehicle to creep at a low speed without a driverinput torque demand. The DISG may propel the vehicle up to a thresholdwheel torque level and then the engine may be started so that the DISGand engine provide torque to the driveline at higher requested desiredwheel torques. In other examples, the DISG and the engine may propel theengine upon releasing the vehicle brake depending on the battery SOC.Method 400 proceeds to 410 after the DISG is allowed to propel thevehicle without the engine after brake pedal release.

At 410, method 400 judges whether or not manual control (e.g., controlby the vehicle driver) of the engine, driveline disconnect clutch, andmotor are requested. A manual request for control may be made via asdisplay input or via a switch or other known user interface. If method400 judges that manual control over the engine, driveline disconnectclutch, and motor are requested, the answer is yes and method 400proceeds to 470 of FIG. 10. Otherwise, the answer is no and method 400proceeds to 411.

Turning now to FIG. 10, method 400 judges whether or not manual controlover the driveline disconnect clutch is requested at 470. In oneexample, method 400 may judge that manual control over the disconnectclutch is desired in response to a driver input. If method 400 judgesthat manual control over the driveline disconnect clutch is requested ordesired, the answer is yes and method 400 proceeds to 471. Otherwise,the answer is no and method 400 proceeds to 473.

At 471, method 400 judges whether or not the driver is requesting thatthe driveline disconnect clutch be locked in a closed position. Method400 may determine that the driveline disconnect clutch is beingrequested to be locked in a closed position in response to a user inputfrom the driver. If method 400 judges that it is desired to lock thedisconnect clutch in a closed position, the answer is yes and method 400proceeds to 472. Otherwise, the answer is no and method 400 proceeds to473. If method 400 proceeds to 400 the driveline disconnect clutch isoperated automatically and not in response to a specific driver requestto open or close the driveline disconnect clutch.

At 472, method 400 closes the driveline disconnect clutch and leaves itlock in a closed state until the driver releases manual control over thedriveline disconnect clutch. Closing the driveline disconnect clutchmechanically couples the engine to the DISG, but the DISG and/or enginemay be deactivated when the driveline disconnect clutch is closed.Method 400 proceeds to 473 after the driveline disconnect clutch isclosed.

At 473, method 400 judges whether or not DISG only operation isrequested. In DISG only operating mode the engine is deactivated bystopping fuel flow to the engine. The engine throttle may also be closedand cam timing/lift is adjusted to a lower volumetric efficiency whenthe engine is deactivated to increase pumping losses and to reduce airflow through the engine. Alternatively, the throttle may be opened andthe cam timing/lift may be adjusted to a higher volumetric efficiency toreduce engine pumping losses. DISG only operation may be manuallyselected by the driver. If DISG only mode is requested the answer is yesand method 400 proceeds to 474. Otherwise, the answer is no and method400 proceeds to 478.

At 474, method 400 opens the driveline disconnect clutch to reducerotational losses, thereby increasing the amount of energy that isavailable to propel the vehicle. If the driveline disconnect clutch hasbeen manually closed, entry into DISG only mode may be inhibited. Method400 proceeds to 475 after the driveline disconnect clutch has beenopened.

At 475, method 400 judges whether or not battery SOC is less than athreshold SOC. In one example, the threshold SOC is at a level thatallows the engine to be restarted via the DISG or another starter. Thebattery SOC may be determined from battery voltage. If method 400 judgesthat battery SOC is less than a threshold SOC, the answer is yes andmethod 400 proceeds to 476. Otherwise, the answer is no and method 400proceeds to 480.

At 476, method 400 restarts the engine. The engine is restarted so thatthe DISG may change modes from providing positive torque to thedriveline to absorbing torque from the driveline and producingelectrical energy to recharge the batteries. In other examples, the DISGmay simply be shutdown without starting the engine after the operator isprovided an indication of an impending DISG shutdown. Method 400proceeds to 477 after the engine is restarted.

At 477, method 400 changes the DISG mode to a mode where electricalenergy is provided to batteries from the DISG. However, if the enginelacks torque to provide a torque requested by the driver, an indicationthat the DISG is unavailable is provided to the driver. Otherwise, theengine provides torque based in the driver torque request and batterycharging via the DISG. Method 400 proceeds to 480 after the DISG mode ischanged.

At 478, method 400 judges whether or not engine only mode is manuallyrequested by the driver. In engine only mode the driveline disconnectclutch is closed and the DISG is not providing positive torque to thedriveline. However, in some examples, the DISG may be providing anegative torque to the driveline to recharge batteries and provideelectrical power to the vehicle's electric network. If engine only modeis manually requested by the driver, the answer is yes and method 400proceeds to 479. Otherwise, the answer is no and method 400 proceeds to480.

At 479, method 400 deactivates the DISG from providing positive torqueto the driveline. However, in some examples, the DISG may convertrotational energy from the engine into electrical energy to chargevehicle batteries and provide electrical power to the vehicle's electricnetwork. Method 400 proceeds to 480 after the DISG is deactivated.

At 480, method 400 judges whether or not a request to enter a hilldecent mode has been requested. In some examples, a hill assent mode maybe provided in place of or in addition to the hill descent mode at 480.In a hill descent mode the engine and DISG may provide a higher level ofvehicle braking than when the vehicle is not in a hill descent mode. Arequest to enter a hill descent mode may be manually be input by thedriver. Alternatively, hill descent mode may be entered when the vehicleinclinometer indicates a negative driving surface grade that is steeperthan a threshold negative grade. If a request for hill descent mode isrequested, the answer is yes and method 400 proceeds to 481. Otherwise,the answer is no and method 400 proceeds to 482. In examples including ahill assent mode, the driveline disconnect clutch is operated in asimilar manner.

At 481, method 400 closes the disconnect clutch to mechanically couplethe engine to the DISG and vehicle braking is increased via increasedengine braking and DISG braking. In one example, engine braking isincreased by adjusting engine valve timing. DISG braking is increase byallowing more field current to be supplied to the DISG. In one example,the rate of DISG braking and engine braking is adjusted responsive tothe driving surface grade. For example, if the road surface is deemedmore slick than a threshold, the rate of DISG and engine braking may bereduced. Method 400 proceeds to 482 after DISG and engine braking areadjusted.

At 482, method 400 allows the driver to manually input engine stopconditions. Additionally, method 400 stops the engine responsive to themanually input stop conditions. For example, the driver may input aperiod of time after the vehicle reaches zero speed before enginerotation may be automatically stopped. In another example, the drivermay specify a threshold battery SOC where engine rotation may beautomatically stopped. In still another example, the driver may specifythat the engine is not stopped when the ascending or descending grade issteeper than a specified value. Method 400 proceeds to 483 after thedriver is allowed to manually input engine stopping conditions and afterthe engine stopping conditions are implemented.

At 483, method 400 allows the driver to manually input DISG operatingmode conditions. Further, method 400 operates the DISG responsive to themanually input conditions. For example, the driver may input a wheeltorque demand level below which the DISG is operated without supplyingfuel to the engine. In another example, the driver may specify athreshold torque above which the DISG assists the engine to provide thedesired wheel torque. In still another example, the driver may specifythat the DISG is to being providing electrical energy to the batterieswhen the battery SOC is less than a driver input level. Method 400proceeds to 484 after the driver is allowed to manually input DISGoperating conditions.

At 484, method 400 allows the driver to manually input drivelinedisconnect clutch opening and closing conditions. For example, thedriver may input a condition that the driveline disconnect clutch beclosed in response to a particular driveline mode (e.g., hold disconnectclutch closed in 4×4 low mode and selectively closed disconnect clutchin 4×2 and 4×4 high modes). In another example, the driver may input acondition that the driveline disconnect clutch be opened in response toan engine idle time duration. In still another example, the driver mayspecify driveline disconnect clutch to be closed when battery SOC isless than a driver specified value. Method 400 exits after the driver isallowed to manually input engine, driveline disconnect clutch, and motorcontrol conditions.

Returning now to FIG. 4, method 400 operates the engine, drivelinedisconnect clutch, and DISG according to adjusted base automatedconditions. Specifically, base calibrated engine, driveline disconnectclutch, and DISG operating conditions are the basis for operating theengine, driveline disconnect clutch, and DISG except where specificdriver changes in the above sections of method 400 have been input. Forexample, if the driver requested PTO operation and that the DISG isoperated until battery SOC reaches a driver specified level, the engine,driveline disconnect clutch, and DISG are operated according to basecalibrated conditions except when the vehicle is in a PTO mode using theDISG. Method 400 exits after the engine, driveline disconnect clutch,and DISG are operated according to adjusted base operating modeconditions.

Thus, the method of FIGS. 4-10 provide for adjusting operation of ahybrid vehicle, comprising: adjusting a schedule for automaticallystopping engine rotation in response to a condition of a drivingsurface. The method includes where the condition of the driving surfaceis a measure surface roughness. The method also includes where thecondition of the driving surface is a measure of frequency of turns. Inthis way, engine rotation may be stopped when road conditions are goodand engine rotation may continue when road conditions have degraded.Consequently, fuel consumption can be reduced during conditions wherethe driver is less likely to need additional torque from the engine.

In one example, the method further comprises adjusting the schedule inresponse to a road condition metric. The method further comprisesadjusting opening of a driveline disconnect clutch in response to thecondition of the driving surface. The method includes where opening ofthe driveline disconnect clutch is according to a first schedule inresponse to the hybrid vehicle being in a two wheel drive mode, andwhere opening the driveline disconnect clutch is according to a secondschedule, the second schedule different from the first schedule, inresponse to the hybrid vehicle being in a four wheel drive mode. Themethod further comprises automatically restarting an engine in responseto the condition of the driving surface degrading to a threshold level.

In another example, the method of FIGS. 4-10 includes adjustingoperation of a hybrid vehicle, comprising: adjusting a first schedulefor automatically idling an engine and decoupling the engine from adriveline in response to a condition of a driving surface. The methodincludes where the driveline includes a DISG located in the driveline ofthe hybrid vehicle. The method also includes automatically restartingthe engine in response to the condition of the driving surface degradingto a threshold level. The method includes where the first schedule isapplied when the hybrid vehicle is operated in a two wheel drive mode.The method further comprises a second schedule that is applied when thehybrid vehicle is operated in a four wheel drive mode. In anotherexample, the method further comprises adjusting the second schedule forautomatically idling an engine and decoupling the engine from adriveline in response to a condition of a driving surface. The methodfurther comprises allowing the engine to stop rotating in response tothe condition of the driving surface.

The method of FIGS. 4-10 also includes adjusting operation of a hybridvehicle, comprising: adjusting operation of a driveline disconnectclutch positioned in a hybrid vehicle driveline in response to a closingrate of an obstruction in a path of the hybrid vehicle. The methodfurther comprises further adjusting operation of the drivelinedisconnect clutch in response to operating the hybrid vehicle in a fourwheel drive mode. The method further comprises further adjustingoperation of the driveline disconnect clutch in response to a conditionof a driving surface. The method further comprises restarting an enginein response to the closing rate of the obstruction. The method includeswhere the driveline disconnect clutch is positioned between an engineand a DISG. The method includes where adjusting operation of thedriveline disconnect clutch includes closing the driveline disconnectclutch in response to the closing rate being greater than a threshold.

Referring now to FIG. 11, a prophetic example sequence for operating avehicle that includes a PTO is shown. The sequence of FIG. 11 may beprovided by the method of FIG. 4 executed in the system of FIGS. 1-3.FIG. 11 shows an example of PTO operation where the DISG solely suppliestorque to the PTO. However, in some examples, the engine may also supplyPTO torque.

The first plot from the top of FIG. 11 shows a PTO request versus time.The X axis represents time and the Y axis indicates PTO operationalrequest state. A lower level PTO signal indicates an absence of a PTOoperating request. A higher level PTO signal indicates presence of a PTOoperating request. Time increases from the left side of the plot to theright side of the plot.

The second plot from the top of FIG. 11 shows battery state of chargeversus time. The X axis represents time and the Y axis indicates batterystat of charge. Battery state of charge increases in the direction ofthe Y axis arrow. Time increases from the left side of the plot to theright side of the plot. Horizontal line 1101 represents a minimumbattery SOC where the DISG is operated.

The third plot from the top of FIG. 11 shows a PTO direction requestversus time. The X axis represents time and the Y axis indicates PTOdirection request state. A lower level PTO direction request signalindicates to rotate the PTO in a forward direction (e.g., rotate to theright). A higher level PTO direction request signal indicates to rotatethe PTO in a reverse direction (e.g., rotate the PTO to the left). Timeincreases from the left side of the plot to the right side of the plot.

The fourth plot from the top of FIG. 11 shows PTO rotation directionversus time. The X axis represents time and the Y axis indicates PTOdirection. A lower level PTO direction signal indicates PTO rotation ina forward direction (e.g., rotate to the right). A higher level PTOdirection signal indicates PTO rotation in a reverse direction (e.g.,rotate the PTO to the left). Time increases from the left side of theplot to the right side of the plot.

The fifth plot from the top of FIG. 11 shows PTO torque versus time. TheX axis represents time and the Y axis indicates PTO output torque. PTOpositive output torque increases in the direction of the Y axis arrow.Time increases from the left side of the plot to the right side of theplot. In this example, PTO output torque is always shown as positive,independent of PTO rotation direction, since the PTO is supplying torqueto an external device.

The sixth plot from the top of FIG. 11 shows DISG torque versus time.The X axis represents time and the Y axis indicates DISG output torque.DISG positive output torque increases in the direction of the Y axisarrow. Time increases from the left side of the plot to the right sideof the plot. In this example, DISG output torque is always shown aspositive, independent of PTO rotation direction, since the DISG issupplying torque to an external device via the PTO.

At time T₀, the PTO request is at a low level indicating the absence ofa PTO request and PTO output. The battery state of charge is at arelatively high level indicating that the PTO may operate for someperiod of time solely under battery power. The PTO direction requestsignal indicates that the PTO is to operate in a forward direction whenthe PTO is engaged. The PTO direction also indicates that the PTO willrotate in a forward direction if engaged. The PTO output torque at zerosince the PTO is not engaged and the DISG torque is also shown at zero.

At time T₁, the PTO request signal transitions to a higher level toindicate that the PTO should be engaged in response to a driver orcontroller request. The PTO request signal may transition in response toan operator input or a controller request for PTO output. The batterystate of charge begins to slowly be reduced as the DISG outputincreases, thereby increasing the PTO torque. The PTO direction requestremains in a forward direction and the PTO rotates in a forwarddirection as indicated by the PTO direction plot.

At time T₂, the PTO direction request transitions from forward toreverse in response to a driver or controller request. The PTO directionchanges from forward to reverse shortly after the DISG and PTO torqueare reduced so as to accommodate the change in PTO direction. The PTOand DISG torque is reduced to avoid producing a torque disturbance tothe driveline. The battery state of charge continues to be reduced asDISG operation continues.

At time T₃, the PTO request is still asserted, but the battery SOC isreduced to the minimum state of charge 1101 where DISG operation ispermitted. Consequently, the DISG output torque and PTO torque arereduced in response to the battery SOC. The PTO direction and PTOdirection request remain in a reverse state. By ramping off the DISG,battery degradation may be avoided.

In this way, a driveline including a DISG and PTO may be operated toprovide direction control. Further, PTO operation may be limited so asto reduce the possibility of battery and/or DISG degradation.

Referring now to FIG. 12, a prophetic example sequence for operating avehicle that includes a 4×4 low gear range mode is shown. The sequenceof FIG. 12 may be provided by the method of FIG. 4 executed in thesystem of FIGS. 1-3.

The first plot from the top of FIG. 12 shows a 4×4 low gear rangerequest versus time. The X axis represents time and the Y axis indicates4×4 low gear range request state. A lower level 4×4 low gear rangesignal indicates an absence of a 4×4 low gear range operating request. Ahigher level 4×4 low gear range signal indicates presence of a 4×4 lowgear range operating request. Time increases from the left side of theplot to the right side of the plot.

The second plot from the top of FIG. 12 shows desired wheel torqueversus time. The X axis represents time and the Y axis representsdesired wheel torque. Desired wheel torque increases in the direction ofthe Y axis arrow. Time increases from the left side of the plot to theright side of the plot.

The third plot from the top of FIG. 12 shows engine operating stateversus time. The X axis represents time and the Y axis indicates engineoperating state. A lower level engine operating state signal indicatesthat the engine has stopped rotating. A higher level engine operatingstate signal indicates that the engine is rotating under its own power.Time increases from the left side of the plot to the right side of theplot.

The fourth plot from the top of FIG. 12 shows vehicle brake pedal stateversus time. The X axis represents time and the Y axis indicates brakepedal state. A lower level brake pedal signal indicates that the brakepedal is not applied or is released. A higher level brake pedal signalindicates that the brake pedal is applied. Time increases from the leftside of the plot to the right side of the plot.

The fifth plot from the top of FIG. 12 shows engine torque versus time.The X axis represents time and the Y axis indicates engine outputtorque. Engine positive output torque increases in the direction of theY axis arrow. Time increases from the left side of the plot to the rightside of the plot.

The sixth plot from the top of FIG. 12 shows DISG torque versus time.The X axis represents time and the Y axis indicates DISG output torque.DISG positive output torque increases in the direction of the Y axisarrow. Time increases from the left side of the plot to the right sideof the plot.

At time T₀, the 4×4 low gear range request is at a low level indicatingthe absence of a 4×4 low gear range request. Desired wheel torque is ata middle level and the engine is rotating under its own power. The brakeis not applied and the DISG and engine are both providing torque to thevehicle driveline.

At time T₁, the desired wheel torque is reduced in response to a driverreleasing an accelerator pedal. Further, the vehicle brake pedal isapplied by the driver and the engine and DISG torque are reduced inresponse to the reduced desired wheel torque. The engine continues tooperate and 4×4 low gear range has not been requested.

At time T₂, the desired wheel torque reaches zero and the engine isautomatically stopped shortly thereafter without the driver requestingengine stop via a dedicated input having the sole function of startingand/or stopping the engine. The engine state signal transitions to a lowlevel to indicate that the engine has been stopped. The engine torqueand the DISG torque are at a level of zero so that the vehicle is notpropelled. The vehicle brake remains in an applied state.

At time T₃, the 4×4 low gear range is requested as indicated by the 4×4low gear range signal transitioning to a higher level. The 4×4 low gearrange signal may be asserted in response to a driver's request to enter4×4 low gear range. The driveline disconnect clutch (not shown) is alsoclosed at time T₃ in response to entering the 4×4 low gear range.

At time T₄, the vehicle brake state transitions to a lower level inresponse to a driver releasing a brake pedal. Since the vehicle is in a4×4 low gear range, the engine is started automatically without driverinput to a device that has a sole function of starting and/or stoppingthe engine (e.g., a starter switch) in response to the brake pedalrelease. Shortly thereafter, the desired wheel torque increases inresponse to a driver depressing an accelerator pedal. The engine torqueand the DISG torque also increase in response to the increasing desiredwheel torque to provide the desired wheel torque. Thus, the engine isautomatically started in response to brake pedal release when thevehicle is in 4×4 low gear range. Such operation allows the vehicledriveline to receive a higher level of torque. The driveline disconnectclutch remains engaged during the engine stop and restart periods.

Between times T₄ and T₅, engine torque and DISG torque are increased toprovide the desired wheel torque in response to a driver or controllerrequest. Further the brake pedal remains in an inactivated state untilthe brake pedal is applied at time T₅ as indicated by the brake pedalstate transitioning to a higher level. The desired wheel torque signalis also reduced at time T₅ in response to the driver releasing theaccelerator pedal. Further, the engine torque and DISG torque arereduced in response to the reduced desired wheel torque at time T₅. Thevehicle remains in 4×4 low gear range. The engine is shutdown and stopsrotating shortly before time T₆. The amount of time it takes betweenwhen the desired wheel torque reaches zero, when the engine torque isreduced to idle the engine, and DISG torque reaches zero to the timewhen the engine is stopped increases since the vehicle is in the 4×4 lowgear range as compared to when the vehicle is in the 4×2 mode at timeT₂. This additional delay time is useful for allowing a pause timebetween driving over rough driving surfaces without prematurely stoppingthe engine.

At time T₆, the vehicle exits 4×4 low gear range and transitions to 4×2wheel or 4×4 high gear range in response to a driver demand. The brakepedal continues to be applied as indicated by the brake state signalremaining at a higher level. The engine torque and DISG torque remain atlow levels.

At time T₇, the desired wheel torque is increased in response to adriver or controller request. Since the vehicle is now not in 4×4 lowgear range, the engine remains stopped and DISG output torque isincreased to meet the desired wheel torque. Thus, the DISG suppliestorque to the driveline, including creep torque to slowly propel thevehicle without a driver wheel torque demand, up to a threshold torqueso that fuel may be conserved. The vehicle brake is also released by thedriver as indicated by the brake state transitioning to a lower level.

At time T₈, the desired wheel torque is increased to a level where theengine is restarted in response to the desired wheel torque requested bya driver or controller. Engine torque is supplied to the driveline tomeet the desired wheel torque after the engine is started as indicatedby the engine state signal transitioning to a higher level. Thus, theengine and DISG both supply torque to meet the desired wheel torque attime T₈.

In this way, a driveline including a DISG and engine may be operateddifferently when the vehicle is operated in 4×4 low gear range ascompared to when the vehicle is operated in a different driveline mode.Such operation may reduce driveline component degradation by limitingthe number of transitions between applying and releasing the drivelinedisconnect clutch.

Referring now to FIG. 13, a prophetic example sequence for operating avehicle between 4×2 and 4×4 modes is shown. The sequence of FIG. 13 maybe provided by the method of FIG. 4 executed in the system of FIGS. 1-3.

The first plot from the top of FIG. 13 shows a plot of available enginemodes versus time. The X axis represents time and the Y axis indicatesavailable engine mode. When the available engine mode is at a value ofone, the engine may be operated only with the engine coupled to theDISG. Further, when the available engine mode is a value of one, theengine remains rotating. When the available engine mode is at a value oftwo, the driveline disconnect clutch may be in an open or closed state.The engine remains rotating when the engine mode is a value of two, andthe engine may be at idle when the driveline disconnect clutch is open.When the available engine mode is a value of three, engine rotation maycontinue at idle, off-idle, or be stopped to conserve fuel. Theavailable engine modes change in response to the road condition metricdescribed in the second plot. Time increases from the left side of theplot to the right side of the plot.

The second plot from the top of FIG. 13 shows a road condition metric orvalue versus time. The X axis represents time and the Y axis representsroad condition metric. The road condition metric value increases in thedirection of the Y axis arrow. Time increases from the left side of theplot to the right side of the plot. Horizontal lines 1301, 1302, 1303,and 1304 represent different threshold levels of the road conditionmetric where the available driveline mode changes. The road conditionmetric indicated by line 1301 represents a higher value road conditionmetric where the road may be very slick, very curvy, or very rough. Theroad condition metric indicated by line 1302 represents a middle highervalue road condition metric where the road may be slick, very curvy, orrough. The road condition metric indicated by line 1303 represents amiddle lower value road condition metric where the road may be somewhatslick, very curvy, or rough. The road condition metric indicated by line1304 represents a lower value road condition metric where the road isnot very slick, very curvy, or very rough.

The third plot from the top of FIG. 13 shows engine operating stateversus time. The X axis represents time and the Y axis indicates engineoperating state. When the engine state is at a value of one, enginerotation is stopped. When the engine state is at a value of two, theengine operates at idle when the driveline disconnect clutch is open.Further, when the driveline disconnect clutch is closed and the enginestate is a value of two, the engine may operate at idle or off-idle(e.g., at higher engine speeds). When the engine state is at a value ofthree, the engine may operate at idle or off-idle when the drivelinedisconnect clutch is closed. Time increases from the left side of theplot to the right side of the plot.

The fourth plot from the top of FIG. 13 shows driveline mode versustime. The X axis represents time and the Y axis indicates drivelinemode. A lower level driveline mode signal indicates that the drivelineis in 4×2 mode. A higher level driveline mode signal indicates that thedriveline is in 4×4 mode. Time increases from the left side of the plotto the right side of the plot.

The fifth plot from the top of FIG. 13 shows driveline disconnect clutchstate versus time. The X axis represents time and the Y axis indicatesdriveline disconnect clutch state. A higher level driveline disconnectclutch state indicates that the disconnect clutch is closed and theengine is mechanically coupled to the DISG. A lower level drivelinedisconnect clutch state indicates that the disconnect clutch is open andthe engine is not mechanically coupled to the DISG. Time increases fromthe left side of the plot to the right side of the plot.

The sixth plot from the top of FIG. 13 shows wheel torque demand versustime. The X axis represents time and the Y axis indicates desired wheeltorque. Desired wheel torque increases in the direction of the Y axisarrow. Time increases from the left side of the plot to the right sideof the plot.

At time T₀, the available engine mode is at a value of three andindicates that the engine may be stopped, operated at idle, or operatedoff idle. Additionally, the road condition metric is at a level belowthe lower threshold 1304 and the driveline is in 4×2 mode as indicatedby the driveline mode signal being at a lower state. The engine statevalue is at three and indicates that the engine may be operate at idle,off-idle, or may stop since road condition metric is less than the levelindicated by horizontal line 1304.

At time T₁, the road condition metric has increased to a value that isgreater than the level indicated by lines 1304. The road conditionmetric level indicated by line 1304 is a level while in 4×2 mode, theavailable engine mode changes in response to the road condition metricvalue. The road condition metric is changed in response to road orsurface conditions on which the vehicle is operating. The availableengine mode signal changes to a value of two in response to the changein the road condition metric. In particular, the available engine modesare changed such that the engine may be operated at idle or off-idlewith the driveline disconnect clutch open, but the engine may not beautomatically stopped. The disconnect clutch remains closed and thewheel torque demand remains relatively constant. Further, the drivelinemode remains in 4×2 mode.

At time T₂, the road condition metric has increased to a value that isgreater than the level indicated by line 1301. The available engine modesignal changes to a value of one in response to the change in the roadcondition metric. Specifically, the available engine modes are changedsuch that the engine may not be operated at idle with the disconnectclutch open and rotation of the engine may not be automatically stopped.The disconnect clutch remains closed and the wheel torque demand remainsrelatively constant. Further, the driveline mode remains in 4×2 mode.

Between time T₂ and time T₃, the driveline mode is changed from 4×2 to4×4 and the wheel torque is varied in response to driver demand. Theroad condition metric increases to a value above horizontal line 1301.As a result, the available engine mode remains at a value of one toensure that the driveline may be ready to respond to driver input duringdegraded driving conditions. The engine state stays at a value of three,and the driveline disconnect remains closed.

At time T₃, the road condition metric is reduced to a value less thanthat of horizontal line 1301 in response to road conditions. The lowerroad condition metric indicates improving driving conditions. Theavailable engine mode changes to a value of two in response to thedecreasing road condition metric. Further, the wheel torque isrelatively low so that the driveline disconnect clutch may be opened asshown. The engine moves to idle as indicated by the engine statechanging to a value of one. The driveline mode remains in 4×4 mode. Inthis way, engine fuel consumption may be reduced by operating the engineat idle with the driveline disconnect clutch held open. However, theengine may not be automatically stopped when the available engine modeis at a value of two.

At time T₄, the road condition metric is reduced to a level belowhorizontal line 1304 in response to road conditions. Consequently, theavailable engine mode is changed to a value of three to allow the engineto stop. The disconnect clutch remains in an open state and thedriveline mode remains in 4×4 mode. Between time T₄ and time T₅, thewheel torque increases and decreases in response to a drive demand andthe driveline disconnect clutch is closed to provide the desired wheeltorque via a combination of engine and DISG torque. The drivelinedisconnect clutch is closed when the wheel torque exceeds a thresholdlevel shortly before time T₅. The engine state changes from stopped towhere the engine may idle when the disconnect clutch is open. However,since the disconnect clutch is closed, the engine may be operated athigher speeds.

At time T₅, the road condition metric increases to a value indicated byhorizontal line 1304 in response to road conditions. The availableengine mode changes to a value of two to indicate that the engine may beoperated at idle and off-idle but may not be automatically stopped. Itmay be observed that the available engine modes changes at differentlevels of the road condition metric when the vehicle is operated in 4×4mode as compared to when the vehicle is operated in 4×2 mode. Suchoperation may reduce degradation of driveline components when thevehicle is operated in 4×4 mode. The engine state remains at a value oftwo indicating that the engine may go to idle if the disconnect clutchis opened.

At time T₆, the road condition metric value increases to a level greaterthan that of horizontal line 1301. The available engine modes changes toa value of three indicating that the engine may not be automaticallystopped. The engine state is also changes to a level of three toindicate that the engine may operate at idle or off-idle when thedisconnect clutch is closed. The engine state and available engine modestay at the same levels until the end of the sequence.

As will be appreciated by one of ordinary skill in the art, methodsdescribed in FIGS. 4-10 may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various steps orfunctions illustrated may be performed in the sequence illustrated, inparallel, or in some cases omitted. Likewise, the order of processing isnot necessarily required to achieve the objects, features, andadvantages described herein, but is provided for ease of illustrationand description. Although not explicitly illustrated, one of ordinaryskill in the art will recognize that one or more of the illustratedsteps or functions may be repeatedly performed depending on theparticular strategy being used.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas,gasoline, diesel, or alternative fuel configurations could use thepresent description to advantage.

The invention claimed is:
 1. A method of adjusting operation of a hybridvehicle, comprising: adjusting a schedule for automatically stoppingengine rotation in response to a road condition of a driving surface,including maintaining engine idling decoupled from a vehicle drivelineinstead of completely stopping an engine when road conditions havedegraded.
 2. The method of claim 1, where the condition of the drivingsurface is an estimate of surface roughness.
 3. The method of claim 1,where the condition of the driving surface is a measure of frequency ofturns.
 4. The method of claim 1, further comprising adjusting theschedule in response to a road condition metric.
 5. The method of claim1, further comprising adjusting opening of a driveline disconnect clutchin response to the condition of the driving surface.
 6. The method ofclaim 5, where opening of the driveline disconnect clutch is accordingto a first schedule in response to the hybrid vehicle being in a twowheel drive mode, and where opening the driveline disconnect clutch isaccording to a second schedule, the second schedule different from thefirst schedule, in response to the hybrid vehicle being in a four wheeldrive mode.
 7. The method of claim 1, further comprising automaticallyrestarting the engine in response to the condition of the drivingsurface degrading to a threshold level.
 8. A method of adjustingoperation of a hybrid vehicle, comprising: adjusting a first schedulefor automatically idling an engine and decoupling the engine via adisconnect clutch from a driveline in response to a condition of adriving surface; stopping rotation of the engine in response to thecondition of the driving surface and a battery state of charge comparedto a threshold, the threshold based on deceleration conditions.
 9. Themethod of claim 8, where the driveline includes a driveline integratedstarter/generator located in the driveline of the hybrid vehicle. 10.The method of claim 8, further comprising automatically restarting theengine in response to the condition of the driving surface degrading toa threshold level.
 11. The method of claim 8, where the first scheduleis applied when the hybrid vehicle is operated in a two wheel drivemode.
 12. The method of claim 11, further comprising a second schedulethat is applied when the hybrid vehicle is operated in a four wheeldrive mode.
 13. The method of claim 12, further comprising adjusting thesecond schedule for automatically idling the engine and decoupling theengine from the driveline in response to the condition of the drivingsurface.
 14. A method of adjusting operation of a hybrid vehicle,comprising: adjusting operation of a driveline disconnect clutchpositioned in a hybrid vehicle driveline in response to a closing rateof an obstruction in a path of the hybrid vehicle; and automaticallystopping engine rotation in response to vehicle deceleration and batterystate of charge.
 15. The method of claim 14, further comprising furtheradjusting operation of the driveline disconnect clutch in response tooperating the hybrid vehicle in a four wheel drive mode.
 16. The methodof claim 14, further comprising further adjusting operation of thedriveline disconnect clutch in response to a condition of a drivingsurface.
 17. The method of claim 14, further comprising restarting theengine in response to the closing rate of the obstruction.
 18. Themethod of claim 14, where the driveline disconnect clutch is positionedbetween the engine and a driveline integrated starter/generator.
 19. Themethod of claim 14, where adjusting operation of the drivelinedisconnect clutch includes closing the driveline disconnect clutch inresponse to the closing rate being greater than a threshold.